Ultra high frequency electric oscillator



y 7, 1948. s. G. TOMLIN ULTRA HIGH FREQUENCY ELECTRIC OSCILLATOR Filed Dec. 2', r9425 2 Sheets-Sheet 1 FIGS).

S. G. TOMLIN ULTRA HIGH FREQUENCY ELECTRIC OSCILLATOR July 27, 1948.

Filed Dec. 2, 1945 2 Sheets-Sheet 2 I N VEN TOR. STANLEY GOADfl/V 70ML/N Patented July 21, 1948.

ULTRA HIGH FREQUENCY ELECTRIC OSCILLATOR Stanley Gordon Tomlin, London, England, as-

signor to Standard Telephones and Cables Limited, London, England, a British company Application December 2, 1943, Serial No. 512,575 In Great Britain December 4, 1942 "application, specification No. 367,401, filed November 27, 1940, now Patent No. 2,320,860 dated June 1, 1913, issued to J. H. Fremlin. The fre quencygenerated depends on a number of different factors, including the physical dimensions of the resonator, and it is often desirable to be able to adjust the frequency during the operation of the device.- Since, however, the resonator must generally be mounted inside an exhausted envelope, there are considerable mechanical difiiculties in making the adjustment from outside. A method of transmitting a mechanical adjustment through the envelope of an exhausted tube is described in Patent No. 2,368,821 dated Feb. 6, 1945, entitled Mechanical adjustment of elements mounted inside vacuum tubes, which is particularly adapted for the transmission of re- .tations, and the present invention is concerned with an improved tunable resonator which is adaptable for a rotary adjustment.

According to the invention,therefore, there is provided an electron discharge apparatus of the electron velocity modulation type in which a stream of electrons is projected across a gap in a hollow resonator, and in which the said resof nator is tuned by means of a metal vane movable in the neighbourhood of the said gap. l

The invention will be explained in terms of an embodiment illustrated in the accompanying drawing in which:

Fig. 1 shows a longitudinal section of the embodiment;

Fig. 2 shows a transverse section at 2--2 of Fig. 1; and

Fig. 3 shows a perspective view of the frequency adjusting means. i

Fig. 4 shows a longitudinal section of the embodiment at 4-4 of Fig. l enclosed in an envelope.

The tunable resonator shown as an illustration of the invention is mounted inside an exhausted envelope which may be of conventional design, and comprises a cylindrical metal tube l having an enlarged mouth 2 adapted for connection to a dielectric wave guide into which the waves generated are to be propagated. One end of the tube is closed with a tightly fitting metal plug 3. Two diametrically opposite longitudinal slots.

7 Claims. (Cl. 315-),

ATENT OFFICE 2 4 are cut in the walls of the resonator, a complete transverse passage being formed by the fins 5 attached to the walls on either side of the slots and the central plates 6 separated from the fins by the equally spaced gaps l. The plates 6 are supported from the walls of the resonator bythe radial rods 8.

The slots, fins and plates extend for practically the whole length of the resonator l and the transverse passage so formed is therefore shaped like a thin rectangular plate.

Attached to the centre of the plug 3 is a detail 9 formed from a metal strip bent into a skew U-shape so that the upright limbs l0 constitute a pair of parallel staggered vanes one of which is opposite to one of the gaps! on one side of the transverse passage, and the other is opposite another gap on the other side. Thus if the plug 3 be rotated, the vanes may be brought nearer to or further from the corresponding gaps, by which means the capacity shunting the game may be increased or decreased.

As'shown in Fig. 2, the resonator may be excited by firing a thin blade of electrons through the passage by any convenient means indicated conventionally by the cathode ll, control grid l2 and anode l3. This blade of electrons should preferably occupy substantially the whole of the longitudinal depth of the passage. The waves excited in the resonator will have a transverse electric field similar to that of the H11 type wave in circular wave guidesbut there will be substantially no longitudinal electric variation. (See R. L. Lamond, Wave Guides, published. by Methuen, 1942.)

The frequency of the wavesis determined-principally by the transverse dimensions of the resonator, which behaves in some respects similarly to a parallel resonant circuit, of which the equivalent capacity is partly constituted by the capacity at the gaps. This gap capacity is increased or decreased when the vanes are moved nearer to, or further from: the gaps, respectively, so that the resonant frequency will be correspondingly lowered, or raised.

In order-to excite the resonator satisfactorily, the distance along the passage between the two pairs of gaps, and the operating conditions of the electron beam, should be chosen so that the travel time of the electrons is (n periods of' application No. 462,027, filed October 14, 1942,

in connection with Fig. 2 of that specification the 4 adjacent to and generally parallel to the direction of said electron stream, each of said blades being substantially parallel to one of said gaps,

at the base of the enlarged mouth-2 to a bladelike extrusion B6. A glass window I! is 'sealed inside the mouth 2. Cathode l I, control grid IZand anode it are aligned parallel to the passage i,

and rotatable means connected to said metallic element and extending to a point external to said envelope for rotating said U-shaped element to adjust the distance between each of said blades and its adjacent gap.

2. An electric oscillation generator of the velocity modulation type comprising an envelope comprising a cylindrical metal resonator closed at one end and with a pair of slots in the cylinder walls at diametrically opposite points transversely of said cylinder, parallel fins projecting inwardly from the sides of each slot, a pair of spaced parallel plates mounted within said cyl- Connecting leads to these are taken out throughf the sides of the glass envelope, that for anode I 3 shown as lead l8, that for the grid i2 not shown, and that for cathode ll shown connected to the heater l9. Connection to the cathode may be made to either one of the leads 2!] of the heater The plug 3 is preferably operated from the cut-- side of the envelope in which the resonator is mounted by the device described in the above mentioned Patent No. 2,368,821. This device comprises an axial cylindrical metal rod 2! which passes through a thin elastic metal pipe 22 =hermetically sealed through a metal cup 23 sealed to the glass envelope and extending for some, distance outside, the rod being hermetically soldered to the pipe at the outside extremity 24 only. The elasticity of the pipe allows the rod to be twisted through a relatively large angle. Cup 23 is extended exteriorly of the envelope of the discharge device and provides a means for securing the discharge device to a support. The rod 2'] is twisted by a handle 26 which may carry a pointer 21 to give an indication of the angle of twist.

The plug 3 may be rigidly fixed concentrically to the rod just described as shown in Fig. 4. A suitable knob or the like with an index and scale if required may be attached to the external end of the rod. The adjusting device may be designed to give any required amount of movement of the vanes Ill. The plug 3 should be a sufiiciently tight fit in the tube to hold the vanes in any set position against the restoring force of the elastic pipe, and it should, of course, be designed to move smoothly without jerks so that precise adjustments can be easily made. "Alternatively, the rod may be restrained by a suitable separate braking arrangement.

It is, of course, not essential that this method of rotating the plug 3 should be used; any other suitable means may be employed.

It is further to be noted that one of the vanes l0 could be omitted, if desired, as a certain amount of tuning adjustment is possible by means of the other alone.

What is claimed is:

1. An electron discharge apparatus of the velocity modulation type including an envelope containing a hollow resonator designed to support ultra high frequency oscillations and having a wall with a pair of slots, means adjacent one of said slots for projecting a. stream of electrons in a path across the resonator through said slots, said resonator having successive conductivity gaps in the direction of electron flow, a U-shaped metallic element having blades for the arms thereof askew with respect to one another, said metallic element being mounted with said blades inder in line with said parallel fins but spaced longitudinally therefromv defining a longitudinal passage having conductivity-gaps between the said fins and the said plates, means aligned with said slots for projecting a blade-like streamof electrons through said passage and past said gaps, and a movable metal vane mounted along: side one of said gaps and means connected to said metal vane and extended to a point external to said envelope for moving said vane toward or away from the gap. 7

3. A generator according to claimv 2 comprising a second movable vane mounted alongside another of the gaps but on the opposite side ofthe electron stream path and means connected to said metal vanes and extended to a point external to said envelope for simultaneously adjusting the positions of the vanes with respect to the cor: responding gaps.

4. A generator according to claim 2 comprising a second movable vane alongside another of said gaps, a rotatable metal plug closing one end of said resonator and means mounting both vanes on said metal plug whereby a rotation of said plug moves said vanes simultaneously toward or away from the corresponding gaps.

5. An electric oscillation generator of the velocity modulation type comprising anenvelope containing a hollow resonator and provided with a pair of slots in the walls thereof at opposite points transversely of said resonator, parallel fins projecting inwardly from the sides of each slot, 2. pair of spaced parallel plates mounted Within said resonator in line with said parallel fins but spaced longitudinally therefrom defining a longitudinal passage having conductivity gaps between the said fins and the said plates, means aligned with said slots for projecting a blade: like stream of electrons through said passage and past said gaps, a metal vane mounted near at least one of said conductivity gaps, and adjustable means connected to said metal vane and extended to a point external to said envelope for changing the position of, said vane with respect to said one gap to vary its capacity and thus to vary the tuning of said resonator.

6. An electric oscillation generator of the velocity modulation type comprising an evacuated envelope containing a. hollow resonator designed to support ultra high frequency oscillations of a frequency dependent in part on the capacity of its structural parts having a wall with a pair of slots, means aligned with said slots forprojecting a stream of electrons in a path across said resonator through said slots, said resonator having one conductivity gap, a metal plate within said evacuated envelope adjustably mounted in capacitive relation to said gap, means connected to said plate and fitted into one end of said hollow resonator for adjusting the position of said plate to vary its capacitive relation to said resonator part, and. means connected to said means for adjusting the position of said plate and extended to a point external to said envelope for operating said adjusting means, said last-mentioned means comprising a part extending into said envelope and hermetically sealed therein.

7. An electric oscillation generator of the velocity modulation type comprising an evacuated envelope, a hollow cylindrical resonator therein designed to support ultra high frequency oscillations of a frequency dependent in part on the capacity of its structural parts, a rotatable closure plug for said resonator fitted into one end of said cylindrical resonator, a metallic element mounted on said plug in capacitive relation to a part of said resonator and movable with said plug to vary said capacitive relation, a thin elastic pipe hermetically sealed through said envelope, a rod passing through said thin elastic pipe from a point external to said envelope, mean-s attaching said rod to said elastic pipe externally of the REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,222,902 Hahn Nov. 26, 1940 2,259,690 Hansen et a1. Oct. 21, 1941 2,298,949 IIitton Oct. 13, 1942 2,306,282 Samuel Dec. 22, 1942 15 2,306,860 Black Dec. 29, 1942 2,320,860 Fremlin June 1, 1943 2,323,729 Ryan July 6, 1943 2,323,735 Tawney July 6, 1943 2,338,306 Smyth -J; Jan. 4, 1944 FOREIGN PATENTS Number Country Date 537,518 Great Britain June 25, 1941 

